1. Field of the Invention
The present invention relates to a semaphore for use in a detection system and a method of detecting a predetermined state in a high voltage (HV) device, and wherein the predetermined state of the device, when sensed, activates a retroreflective device to reflect infrared signals continuously generated at the device and wherein the reflected signals are indicative that the HV device has reached a predetermined state.
2. Description of Prior Art
In our U.S. Pat. No. 4,451,910 there is described a signalling system which is associated with a high voltage device, herein a disconnect switch, whereby to signal the relative position of a moving contact in relation to a fixed contact. The system as disclosed therein is an ultrasonic system and which has proven extremely expensive to construct, and which may not be efficient during severe weather conditions, such as during a snowstorm, where the reflective surface of the mirrors in the receiver device may be obstructed by snow and ice, and render the receiver inaccurate.
The infrared detecting system of the present invention was conceived for use with a high voltage switch of the type disclosed in the referenced patent and having a fixed contact and a movable contact, and as utilized in an electrical distribution and transport network. However, the detecting system may have other applications with other high voltage devices such as for the monitoring of gas pressure in a high voltage device, or monitoring the level of oil in high voltage devices.
As described in our earlier U.S. Pat. No. 4,451,910, up to now the positions of the contact elements of high voltage disconnect switches have been ascertained by sensing the mechanism which displaces the moving contact blade which is used to close or open the switch. Microswitches are associated with the motorized mechanical connections of the moving contacts to generate signals identifying the position of the moving contact. However, such interconnecting drive mechanisms between the drive motor and the moving contact blade have many flexible connections and are sometimes inaccurate in the operation, and therefore could cause an inaccurate closure of the moving contact, although the microswitches would indicate that the contact is properly closed. Such errors could cause the destruction of the contacts when a strong current passes through the disconnect switch, and in certain cases it is necessary to make visual inspection of the disconnect switch to ascertain the position of its contacts. Therefore, presently known signalling systems are not totally reliable as to the information which they provide and prevent their use in a remote controlled system as often a visual inspection of the disconnect switch would be required.